The present disclosure relates to the use of one or more ion beams to prepare materials for microscopic observation or spectroscopic analysis. Microscopic observational techniques include, but are not limited to, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), reflection electron microscopy (REM). Spectroscopic analysis techniques include, but are not limited to, x-ray micro-analysis, reflection electron energy-loss spectroscopy (REELS), electron back-scattered diffraction (EBSD), x-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES). Materials to be viewed under any microscopic technique may require processing to produce a sample suitable for microscopic examination.
Ion beam milling of a material can produce samples that are well suited for microscopic examination. An ion beam irradiating device may generate, accelerate, and direct a beam of ions toward a sample. The impact of ions on the sample sputters material away from the area of ion impact. Furthermore, the sample surface may be polished by the ion beam to a substantially smooth condition further enhancing observational properties of the sample. Regions of interest in the sample may be exposed and polished by the use of ion beams thus making a suitable observational sample from the material under investigation.
Broad Ion Beam Slope-Cutting (BIBSC), also known as cross section cutting using broad ion beam sources or cross section polishing using broad ion beam sources, is a rapid method for removing sample material to expose a smooth and substantially artifact-free cross-sectional surface for ultimate analysis by various microscopies and spectroscopies. A notable advantage of the BIBSC technique is high rates of surface preparation that can exceed tens or hundreds or thousands of square microns per hour, often over sample milling times of tens or hundreds of minutes.
Important considerations to users of the BIBSC technique include: reducing or minimizing the effort and time that the user is occupied in processing the sample; reducing or minimizing the number of steps where delicate samples are directly handled and at risk for damage, such as during mounting to sample holders for processing or analysis; reducing or minimizing the time and effort the user is occupied transferring the sample into the ultimate analysis equipment (imaging or spectroscopy), and aligning the coordinates of the prepared sample region to the ultimate analysis equipment prior to analysis; ensuring high quality and high probability of success in processing and imaging the sample; reducing or minimizing the time that the BIBSC ion milling equipment and sample mounting equipment are occupied for each sample; and ensuring high-quality microscopy observation of the sample during sample mounting and ultimate analysis by reducing the working distance required between the sample and the objective or probe-forming lens used for observation.
Ion beam milling takes place in a suitably evacuated environment. While a sample may be loaded and unloaded by the user at atmospheric pressure, ion beam processing must take place under vacuum like conditions. A near-vacuum environment that is suitable for ion beam milling of samples takes time to establish. The time required to obtain a suitably evacuated environment is proportional to the volume that must be evacuated prior to the commencement of ion beam milling. Embodiments of the present disclosure teach apparatus and methods of sample loading and processing that reduce the evacuated volume during sample loading and unloading, thereby enabling greater efficiencies in the processing of samples.
While a sample is being prepared in the ion beam, it may experience heating. Heating may alter the sample in ways that are undesirable. It may be the case, for example, that heating the sample softens or melts the sample, thereby causing alterations in the sample that would not happen if the temperature were maintained in a desirable range. Embodiments of the present disclosure teach apparatus, and methods of using that apparatus, to manage the thermal environment of a sample. Embodiments of improved thermal control over the sample may be beneficially combined with embodiments offering improved sample loading and processing to achieve even greater efficiencies in the processing of samples.
In consideration of the foregoing points, it is clear that embodiments of the present disclosure confer numerous advantages and are therefore highly desirable.